Parties do not exist in isolation, but rather relate to each other: hence, the notion of a "party system" that assumes, justifiably, the characteristics and behavior of one party will have an effect on the others. Deeper down, however, the characteristics of party systems depend significantly on the structure of the societies in which they emerged and developed. A society that is primarily tribal or sharply divided in a number of ethnic or religious groups will not have the same party system as a society in which there has been massive industrialization and opposition between classes has been marked.

Nevertheless, the notion that parties emerge from or depend on basic social groups assumes opportunities exist for parties to develop freely. This is, of course, far from universal. In many countries parties have often been simply prohibited; in others only one party has been allowed...